JPH11249484A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the set temperature controllable to be high while reducing the overshooting of a pressure roller without detecting the temperature of the pressure roller. SOLUTION: This image forming device is provided with a fixing means H having a fixing roller 100 and the pressure roller 200 arranged so as to be opposed to each other, a fixing roller heating means H1 arranged as the roller 100 and a pressure roller heating means H2 arranged at the roller 200, and a recording medium is carried by being interposed between the rollers 100 and 200 and an image formed on the recording medium is fixed by being heated and pressured. Besides, it is provided with a fixing roller temperature detection means S1 detecting the temperature of the roller 100 and a control means K controlling the heating means H1 and H2 to be turned on and off based on the detected temperature of the roller 100.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming a digital image by electrophotography.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine or a facsimile which employs an electrophotographic process (hereinafter simply referred to as an image forming apparatus), an image forming means for forming a toner image on an image carrier and a roller facing the image forming apparatus are provided. There is a fixing device that includes a fixing unit that fixes the image on the recording medium by heating and pressurizing the image while nipping the pair, and a rotating unit that rotates the roller pair.

[0003]

By the way, the fixing means includes a fixing roller and a pressure roller which are arranged opposite to each other, a temperature sensor is provided on the pressure roller, and the surface temperature of the pressure roller is set to a predetermined temperature. When the temperature is lower than the predetermined temperature, the heater is turned on, and when the temperature is higher than a predetermined temperature, the heater is turned off. For this reason, if the fixing roller is, for example, a hard roller type, the rubber thickness of the pressure roller is large in order to increase the nip width (for example, 5
mm), the thermal responsiveness of the pressure roller is poor, and when the surface temperature of the pressure roller is detected and the heating means of the pressure roller is controlled on and off at a predetermined temperature, the rubber inside at the boundary with the core bar overshoots. And the temperature becomes high, causing problems such as rubber peeling.

As a method of reducing overshoot,
It is conceivable to shorten the on / off cycle of the heating means.
Since the fixing roller is a hard roller, in order to maintain a predetermined temperature, the on / off cycle of the heating unit is shorter than that of the pressure roller, and by using this timing to turn on / off the pressure roller heating unit, overshoot can be reduced. . If the off time of the heating means of the fixing roller and the pressure roller is equal, the pressure roller is as low as 110 ° C., for example, due to the heater power amount and the roller configuration of the fixing roller and the pressure roller. There has occurred. Therefore, the power supply amount can be increased and the temperature of the pressure roller can be set higher by making the off-timing of the heating means of the pressure roller longer (delayed) than that of the fixing roller. Further, since the ON / OFF cycle of the fixing roller heating means changes depending on the environmental temperature, it is necessary to change the ON time of the pressure roller accordingly.

Further, since the thermal response is poor if the temperature sensor of the fixing roller is not in contact, the difference between the surface temperature of the fixing roller and the temperature detected by the temperature sensor when the warm-up is completed is as follows.
After warming up, it gradually gets smaller, and after a while the difference is constant. When using such a temperature sensor to control ON / OFF of the heating means of the fixing roller, the control temperature is increased stepwise to correct the control temperature. At this time, when the control temperature increases, the on-timing of the heating means of the fixing roller is advanced, and the off-timing of the heating means of the pressure roller is delayed for a certain time with reference to the off-timing of the heating means of the fixing roller, thereby performing prediction control. In this case, the heating means of the pressure roller remains on, and the temperature of the pressure roller rises.

Further, when the fixing roller is a hard roller, for example, the rubber thickness of the pressing roller is set to be thick (5 mm) in order to secure a nip. To control the temperature of the pressure roller surface, or to rotate the roller in contact with the fixing roller and heat it from the outside of the pressure roller to control the surface temperature of the pressure roller. Did not manage. However, with the increase in speed, in continuous copying after warm-up, if there is a portion where the internal temperature of the pressure roller is low, there has been a problem that fixing failure occurs.

In addition, with the digitization, correction operation of image forming conditions has been performed, and there has been a problem that power during the image forming operation is insufficient. .

The present invention has been made in view of such a point, and the inventions according to claims 1 to 4 do not detect the temperature of the pressure roller and reduce overshoot of the pressure roller, It is an object of the present invention to provide an image forming apparatus capable of controlling a set temperature to be high. Another object of the present invention is to provide an image forming apparatus capable of controlling the pressure roller to a predetermined temperature or less when the temperature of the pressure roller is controlled by the temperature of the fixing roller. And Claim 7 or Claim 8
An object of the present invention is to provide an image forming apparatus that prevents a fixing failure due to a decrease in the temperature of a fixing roller during continuous copying after the completion of warm-up. Claim 9
Another object of the present invention is to provide an image forming apparatus capable of efficiently using power consumption and saving power.

[0009]

Means for Solving the Problems In order to solve the above problems and achieve the object, the present invention has the following constitution.

According to the first aspect of the present invention, there is provided a fixing roller and a pressure roller disposed opposite to each other, a fixing roller heating unit provided on the fixing roller, and a pressure roller heating unit provided on the pressure roller. Comprising a fixing unit having a fixing medium, a recording medium is nipped and conveyed between the fixing roller and the pressure roller,
In an image forming apparatus for fixing an image on a recording medium by heating and pressing, a fixing roller temperature detecting unit for detecting a temperature of the fixing roller, and the fixing roller heating unit based on the detected temperature of the fixing roller. An image forming apparatus comprising: a control unit that controls on / off of a pressure roller heating unit. ].

According to the first aspect of the invention, the fixing roller heating means and the pressure roller heating means are turned on / off based on the detected temperature of the fixing roller, so that the temperature of the pressure roller is not detected, and It is possible to control the set temperature high while reducing the overshoot of the pressure roller. In addition, since a temperature sensor for the pressure roller is not required, downsizing, improvement in assemblability, and cost reduction can be achieved.

According to a second aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein the on / off timing of the pressure roller heating means is based on the on / off timing of the fixing roller heating means. ].

According to the second aspect of the invention, the on / off timing of the pressure roller can be easily set.

According to a third aspect of the present invention, there is provided the image forming apparatus according to the second aspect, wherein the off-timing of the pressure roller heating unit is delayed from the off-timing of the fixing roller heating unit. ].

According to the third aspect of the invention, the power supply amount is increased and the pressure roller temperature is increased by delaying the off-timing of the pressure roller heating means from the off-timing of the fixing roller heating means. Can be set.

According to a fourth aspect of the present invention, there is provided the image forming apparatus according to the third aspect, wherein the delay time varies depending on an ON / OFF cycle time of the fixing roller heating unit. ].

According to the fourth aspect of the present invention, the pressure roller heating means uses the ON / OFF cycle of the fixing roller to change the ON / OFF timing of the pressure roller in accordance with a change in the ON / OFF cycle of the fixing roller. Therefore, overshooting of the pressure roller can be prevented, and the temperature can be controlled to a high temperature. Therefore, it is possible to prevent image defects during continuous copying while ensuring the durability of rubber.

According to a fifth aspect of the present invention, there is provided a fixing roller and a pressure roller which are disposed to face each other, a fixing roller heating means provided on the fixing roller, and a pressure roller heating means provided on the pressure roller. An image forming apparatus comprising: a fixing unit having a fixing unit having a fixing unit, a recording medium sandwiched and conveyed between the fixing roller and the pressure roller, and an image on the recording medium is heated and pressed to fix the image. A fixing roller temperature detecting unit that detects a temperature, a pressing roller temperature detecting unit that detects a temperature of the pressing roller, and a drive control of the pressing roller heating unit when the detected temperature of the pressing roller is equal to or higher than a predetermined temperature. A control unit that stops and controls only driving of the fixing roller heating unit. 』
It is.

According to the fifth aspect of the present invention, when the pressure roller has reached a predetermined temperature or higher, the control of the pressure roller heating means is stopped to suppress an increase in the temperature of the pressure roller. Thus, the image quality can be prevented from lowering, the feeding property can be ensured, and the durability of the rubber of the pressure roller can be improved.

According to a sixth aspect of the present invention, it is preferable that the driving control of the pressure roller heating means is stopped and the drive control of the pressure roller heating means is performed again when the detected temperature of the pressure roller is lower than a predetermined temperature. The image forming apparatus according to claim 5, wherein: ].

According to the sixth aspect of the invention, the temperature of the pressure roller is detected, and when the temperature of the pressure roller exceeds a predetermined temperature, the control of the pressure roller heating means is stopped, and only the temperature of the fixing roller heating means is controlled. When the pressure roller falls below the predetermined temperature, the control of the pressure roller heating means is returned again.

According to a seventh aspect of the present invention, there is provided an image forming apparatus comprising: a fixing roller and a pressure roller each having at least one heating means disposed opposite to each other; and a rotating means for pressing and rotating the fixing roller and the pressure roller. Fixing means having
A fixing roller temperature detecting unit for detecting a temperature of the fixing roller in an image forming apparatus for nipping and conveying a recording medium between the fixing roller and the pressure roller and fixing the image on the recording medium by heating and pressing; An image forming apparatus comprising: a control unit that drives the rotating unit until the fixing roller reaches a predetermined temperature after power is turned on. ].

According to the seventh aspect of the present invention, after the power is turned on, the fixing roller and the pressure roller are pressed and rotated and heated during the warm-up period until the fixing roller reaches a predetermined temperature. The rollers can be set to a higher temperature overall.

According to an eighth aspect of the invention, when the fixing roller reaches a predetermined temperature, the driving of the rotating means is stopped,
The image forming apparatus according to claim 7, wherein the image forming permission signal is displayed on a display unit. ].

According to the eighth aspect of the present invention, when the temperature of the fixing roller is completely warmed up, the pressure roller is also completely warmed up. Therefore, rotation and heating are stopped, and copying is enabled. The noise may be reduced by separating the fixing rotation drive and the conveyance drive, and an image formation permission signal is displayed on the display unit.

According to a ninth aspect of the present invention, there is provided an image forming apparatus for forming a toner image on an image carrier and conveying the image by sandwiching a pair of opposed rollers to fix the image on a recording medium by heating and pressing. Fixing means, rotating means for rotating the roller pair,
An image forming apparatus comprising: a control unit that drives the rotating unit after power is turned on, and stops driving of the rotating unit when the image forming unit is driven. ].

According to the ninth aspect of the present invention, the rotating means is driven after the power is turned on, the driving of the rotating means is stopped when the image forming means is driven, and the power required for forming an image on the image carrier is warmed. By stopping the rotation of the roller pair during the up, the power required for forming an image on the image carrier can be supplemented.

According to a tenth aspect of the present invention, there is provided an image forming apparatus for forming a toner image on an image carrier and conveying the image by sandwiching a pair of opposed rollers to fix the image on a recording medium by heating and pressing. An image forming apparatus comprising: a fixing unit; and an image forming apparatus, comprising: at least one heating unit of the fixing unit; and a control unit configured to control a power supply amount to the heating unit when the image forming unit is driven. Forming equipment. ].

According to the tenth aspect of the present invention, by controlling the amount of power supply to the heating means when the image forming means is driven, power consumption can be efficiently used during image formation during warm-up, and power can be saved. Can be achieved.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction and operation of an image forming apparatus according to the present invention will be described below with reference to the drawings. However, the present invention is not limited to the embodiments described below.

FIG. 1 is a sectional view showing an embodiment of the image forming apparatus.

First, a normal copying operation of the staff member forming apparatus will be described. This image shaping device includes an image reading unit 10, a writing unit 20 which is a digital writing system, an image forming unit 30, a paper feeding unit 40, a document placing unit 50, and the like.

On the upper part of the image forming apparatus, a document table 51 made of a transparent glass plate or the like, and a document table 52 including a document cover 52 for covering the document D placed on the document table 51, and the like.
And an image reading unit 10 including a first mirror unit 12, a second mirror unit 13, an image pickup lens 14, an image pickup device 15 such as a CCD array, and the like are provided below the document table 51 and inside the apparatus main body. Have been.

The image of the original D on the original table 51 is transmitted to the illumination lamp 12 A of the image reading unit 10 and the first mirror 12.
B from the solid line to the position shown by the dashed line, and the first mirror unit 12 of the second mirror unit 13 integrally including the second mirror 13A and the third mirror 13B facing each other. The entire surface is illuminated and scanned by the following movement at half the speed with respect to the first mirror 12B and the second mirror 13 by the imaging lens 14.
A, an image is formed on the image sensor 15 via the third mirror 13B. When scanning is completed, the first mirror unit 12 and the second mirror unit 13 return to their original positions,
It waits for the next image formation.

The image data obtained by the photoelectric conversion by the image pickup device 15 is converted into a digital signal, then subjected to image processing by an image signal processing section 60, and is temporarily stored in a memory 61 as an image signal. Next, the image signal is read out from the memory 61 under the control of the CPU 62, subjected to pulse width modulation, and then input to the writing unit 20.

The image forming section 30 outputs an image signal under the control of the CPU 62 to the drive motor 27 and the polygon mirror 2.
2. When input to the writing unit 20 including the fθ lens 23, mirrors 24, 25 and 26, a semiconductor laser (not shown), a correction lens 24B, and the like, an image recording operation is started. That is, the photosensitive drum 31 serving as an image bearing member rotates clockwise as shown by the arrow, and the static elimination performed by performing the pre-charge exposure and eliminating the static electricity is performed by the static eliminator 36, and then the charging device 32
, The writing unit 2
At 0, an electrostatic latent image corresponding to the image of the original D is formed on the photosensitive drum 31 by the laser beam L. Thereafter, the electrostatic latent image on the photosensitive drum 31 is subjected to reversal development by a developer carried on a developing sleeve 33A, which is a developer carrying body to which a bias voltage of a developing unit 33 is applied, and a visible toner It becomes an image.

On the other hand, transfer papers P of a designated size are carried out one by one by a carry-out roller 42A from a paper feed cassette 41A or 41B loaded in a paper feed unit 40, and are carried out by a carry-out roller 43A.
Then, the sheet is fed toward the image transfer section via the guide member 42. The fed transfer paper P is sent onto the photosensitive drum 31 by a registration roller 44 that operates in synchronization with the toner image on the photosensitive drum 31. The toner image on the photosensitive drum 31 is transferred to the transfer paper P by the operation of the transfer unit 34, and is separated from the photosensitive drum 31 by the charge eliminating operation of the separator 35, and then fixed via the transport belt 45. After being sent to the device 37 and fused and fixed by the fixing roller 100 and the pressure roller 200,
The sheets are ejected to a tray 54 outside the apparatus by 8, 46. 53
Denotes a manual paper feed tray.

The photosensitive drum 31 continues to rotate further, and the toner remaining on the surface thereof without being transferred is removed and cleaned by a cleaning blade 39A that is pressed against the surface of the cleaning device 39, and the charge is removed again by the charge remover 36. Upon receiving the charge by the device 32 as described above, the process for the next image formation is started.

The stirring screw 33C of the developing device 33
The magnetic permeability sensor TS provided at the bottom of the monitor monitors the toner density of the developer in the developing device 33 by utilizing the fact that the magnetic permeability changes when the toner density of the developer changes, and the CPU 62 controls the CPU 62 to measure the toner density of the developer. It is a sensor that sends out information. CP
U62 sends a toner replenishing instruction to the toner replenishing unit when the toner replenishment decreases to a certain value or less based on the information of the magnetic permeability sensor TS, and replenishes the toner. Therefore, the toner concentration of the developer can be always kept constant. it can.

Next, the fixing device 37 will be described with reference to FIG. FIG. 2 is a sectional view showing the fixing device.

A pressure roller 200 and a fixing roller 100 are arranged in a casing 300 of the fixing device 37. The pressure roller 200 has a SUS cylinder 230 provided with a silicon rubber layer 231, and a single heater 232 is disposed inside the cylinder 230. Fixing roller 100
Is provided by coating an aluminum cylinder 140 with a resin layer 141, and two heaters 142 are disposed inside the aluminum cylinder 140.

The oil of the oil application pad 150 is applied to the fixing roller 100 by the oil application roller 151.
The recording paper can be easily peeled off at the time of fixing. The fixing roller 100 includes a cleaning roller 152.
Are disposed in contact with each other, and remove the peeling residue, dust, and the like of the toner that forms the image attached to the fixing roller 100.

Guide plates 153 and 154 are provided upstream of the pressure roller 200 and the fixing roller 100 in the direction of conveyance of the recording paper, and guide plates 153 and 154 for guiding the conveyance of the recording paper. And a lower fixing claw 156 are provided.

Further, a temperature detecting sensor as fixing roller temperature detecting means S1 is provided in the vicinity of the fixing roller 100. Based on temperature information obtained from this temperature detecting sensor, the CPU 62 controls the heater 232 of the pressure roller 200 based on the temperature information.
In addition, the control of the heater 142 of the fixing roller 100 is performed.

Next, the configuration of the image forming apparatus according to the present invention will be described.

The image forming apparatus includes a fixing roller 100 and a pressure roller 200 which are disposed opposite to each other, and a fixing roller 10
0, and a fixing unit H having a heater 232 as a pressing roller heating unit H2 provided on the pressing roller 200. The fixing roller 100 includes two heaters 142 serving as fixing roller heating units H1 provided on the pressing roller 200. The transfer paper P, which is a recording medium, is nipped and conveyed between the pressure rollers 200, and the image on the recording medium is heated and pressed to be fixed.

The image forming apparatus has a fixing roller temperature detecting means S1 for detecting the temperature of the fixing roller 100, and ON / OFF control of the fixing roller heating means H1 and the pressure roller heating means H2 based on the detected temperature of the fixing roller 100. And a CPU 62 serving as control means K for performing the control. If the fixing roller 100 is a hard roller type, the rubber temperature of the pressure roller 200 is large in order to increase the nip width, and the thermal response of the pressure roller 200 is poor, so that the surface temperature of the pressure roller 200 is detected. When the on / off control is performed at a predetermined temperature,
The inside of the rubber at the boundary with the core bar overshoots, causing problems such as rubber peeling.

As a method of reducing this overshoot, it is conceivable to shorten the on / off cycle as shown in FIG. Since the fixing roller 100 is a hard roller,
The on / off cycle is shorter than that of the pressure roller 200, and this timing can be used, and overshoot can be reduced.

The fixing roller 100 and the pressure roller 20
When the OFF time is equal to 0, the pressure roller 200 is as low as 110 ° C. due to the amount of heater power and the roller configuration, and image failure during continuous copying has occurred. That is, FIG.
0 indicates the ON / OFF cycle and ON time of the pressure roller heating means H2 and the surface temperature of the pressure roller.
In the on-off cycle and on-time when 0 is 200 ° C., the surface temperature of the pressure roller 200 is 110 ° C., so that it is equal to the on-off cycle of the fixing roller 100 and the pressure roller is maintained at 110 ° C. or more. It is necessary to lengthen the ON time of the pressure roller heating means H2.

Therefore, as shown in FIG. 5, on / off control of the fixing roller heating means H1 and the pressure roller heating means H2 is performed.

The power supply amount was increased and the temperature of the pressure roller was set high by making the ON time of the pressure roller heating means H2 longer (delayed) than that of the fixing roller heating means H1. Further, since the temperature cycle of the fixing roller changes depending on the environmental temperature, it is necessary to change the ON time of the pressure roller.

As described above, the on / off control of the fixing roller heating means H1 and the pressure roller heating means H2 based on the detected temperature of the fixing roller 100 makes it possible to detect the temperature of the pressure roller 200 without detecting the temperature of the pressure roller 200. It is possible to control the set temperature high while reducing overshoot. Further, since a temperature sensor for the pressure roller 200 is not required, downsizing, improvement in assemblability, and cost reduction can be achieved.

The control means K includes a fixing roller heating means H
1 and the pressure roller heating means H2 are turned on and off, and the pressure roller heating means H2 is turned on and off at the timing of the fixing roller heating means H1 because the temperature sensor of the pressure roller 200 is not required. Size reduction, improvement in assemblability, and cost reduction can be achieved.

Further, the off-timing of the pressing roller heating means H2 is delayed from the off-timing of the fixing roller heating means H1, and the off-timing of the pressing roller heating means H2 is changed from the off-timing of the fixing roller heating means H1. By the delay, the power supply amount can be increased and the pressure roller temperature can be set high.

The delay time of the pressure roller heating means H2 depends on the time of the on / off cycle of the fixing roller heating means H1, and the pressure roller heating means H2 uses the on / off cycle of the fixing roller and turns on. By delaying the time from that of the fixing roller, overshoot of the pressure roller can be prevented and the temperature can be controlled to a high temperature. Therefore, it is possible to prevent image defects during continuous copying while ensuring the durability of the rubber.

Next, a specific embodiment of the image forming apparatus will be described.

The fixing roller has a core metal thickness of 13 mm and an internal heater (900 W + 230 W) of the fixing roller heating means H1.
It is. The pressure roller has a core metal thickness of 5 mm and a rubber thickness of 5 m
m, internal heater of pressure roller heating means H2 (280 W)
It is.

The continuous power supply time / on / off cycle time of the fixing roller heating means H1 and the pressure roller heating means H2 for controlling on / off of the fixing roller heating means H1 and the pressure roller heating means H2 to maintain them at a predetermined temperature is as follows. As 70 seconds,
Tables 1 and 2 show the results of changing the roller set temperature, the continuous power supply time, and the delay time.

Table 1

[0060]

Table 2

[0062]

By using the ON / OFF cycle of the fixing roller and delaying the ON time from that of the fixing roller,
Since the overshoot of the pressure roller can be prevented and the temperature can be controlled to a high temperature, it is possible to prevent image defects during continuous copying while ensuring the durability of the rubber. Further, since a temperature sensor for the pressure roller is not required, miniaturization, improvement in assemblability, and cost reduction can be achieved.

FIG. 6 is a flowchart of the heating control of the image forming apparatus according to the first to fourth aspects.

The image forming apparatus of this embodiment reads the fixing roller temperature Ta from the fixing roller temperature detecting means S1 in step a1, and determines in step b1 whether the fixing roller temperature Ta is lower than the set temperature Tl. If the temperature is lower than the set temperature Tl, the fixing roller heating means H
The heater 1 and the heater as the pressure roller heating means H2 are turned on (step c1).

If the fixing roller temperature Ta is not lower than the set temperature Tl in step b1, the heater as the fixing roller heating means H1 is turned off (step d1), and the time C is read (step e1). In step f1,
When the time C reaches the set time C0, the pressure roller heating means H
The heater No. 2 is turned off (step g1).

As described above, based on the detected temperature of the fixing roller, the fixing roller heating means H1 and the pressure roller heating means H2
By controlling the ON / OFF of the pressure roller, the temperature of the pressure roller is not detected, and the set temperature can be controlled to be high while reducing the overshoot of the pressure roller. In addition, since a temperature sensor for the pressure roller is not required, downsizing, improvement in assemblability, and cost reduction can be achieved.

Next, the configuration of the image forming apparatus according to the fifth and sixth aspects will be described.

The image forming apparatus of this embodiment is configured as shown in FIG. 7, and the same components as those of the embodiments of FIGS. 1 and 2 are denoted by the same reference numerals and description thereof is omitted.

The image forming apparatus of this embodiment has a fixing roller temperature detecting means S for detecting the temperature of the fixing roller 100.
1, a pressure roller temperature detecting means S2 for detecting the temperature of the pressure roller 200, and a drive control of the pressure roller heating means H2 based on the detected temperature of the fixing roller 100, and based on the detected temperature of the pressure roller 200. And control means K for stopping the drive control of the pressure roller heating means H2. FIG.
As shown in the figure, the pressure roller 200 is at or above a predetermined temperature (16
0 ° C. or more), pressurizing roller heating means H
By stopping the control in step 2, it is possible to suppress an increase in the temperature of the pressure roller, to prevent a decrease in image quality, to secure feeding performance, and to improve the durability of the rubber of the pressure roller.

After the drive control of the pressure roller heating means H2 is stopped, the drive control of the pressure roller heating means H2 is performed again based on the detected temperature of the pressure roller 200. The temperature of the pressure roller 200 is detected, and when the temperature exceeds a predetermined temperature,
The control of the pressure roller heating means H2 is stopped, only the temperature of the fixing roller heating means H1 is controlled, and when the temperature falls below the predetermined temperature, the control of the pressure roller heating means H2 is returned.

That is, when the temperature sensor of the fixing roller 100 has a poor response such as a non-contact type, as shown in FIG. 9, the power is turned on and the warm-up is performed. After the warm-up, the difference gradually decreases, and after a while, the difference becomes constant. When temperature control is performed using such a temperature sensor, the control temperature is increased stepwise to correct the control temperature. At this time, when the control temperature increases, the on-timing of the fixing roller heating means H1 is quick, and the off-timing of the pressure roller heating means H2 is delayed with reference to the off-timing of the fixing roller heating means H1 to perform predictive control. As a result, the pressure roller heating means H2 remains on, causing a problem that the temperature of the pressure roller rises. Therefore, the temperature of the pressure roller is detected by the pressure roller temperature detection means S2, and when the temperature of the pressure roller reaches a predetermined temperature or more, the control of the pressure roller 200 of the pressure roller heating means H2 is stopped, and only the temperature of the fixing roller 100 is controlled. Then, when the pressure roller temperature falls below the predetermined temperature, the control of the pressure roller is resumed.

Table 3 shows the stepwise temperature control of the fixing roller.
At t = 0, the warm-up is completed.

Table 3

[0075]

In this embodiment, when the pressure roller has reached a predetermined temperature or higher, the control of the pressure roller heater is stopped, so that the temperature rise of the pressure roller can be suppressed, the image quality can be prevented from lowering, and the feeding can be prevented. Performance and the durability of the pressure roller rubber can be improved.

FIG. 10 is a flowchart of the heating control of the image forming apparatus according to the fifth and sixth aspects.

The image forming apparatus of this embodiment reads the pressure roller temperature Tb from the pressure roller temperature detecting means S2 in step a2. In step b2, it is determined whether the pressure roller temperature Tb is lower than the set temperature T2. If the temperature is lower than the set temperature T2, the fixing roller temperature Ta is read from the fixing roller temperature detecting means S1 (step c2). At step d2, it is determined whether or not the fixing roller temperature Ta is lower than the set temperature T1. If the temperature is lower than the set temperature T1, the heater serving as the fixing roller heating means and the heater serving as the pressure roller heating means are turned on ( Step e
2).

If the fixing roller temperature Ta is equal to or higher than the set temperature Tl in step d2, the heater serving as the fixing roller heating means is turned off (step f2), and time C is read (step g2). When the time C reaches the set time C0 in Step h2, the heater serving as the pressure roller heating means is turned off (Step i2).

If the pressure roller temperature Tb is equal to or higher than the set temperature T2 in step b2, the heater serving as the pressure roller heating means H2 is turned off (step j2), and the fixing roller temperature Ta from the fixing roller temperature detecting means S1 is detected. Is read (step k2), and the fixing roller temperature Ta is read in step l2.
Is lower than the set temperature T1.
If not, the heater serving as the fixing roller heating unit H1 is turned off (step m2). If the fixing roller temperature Ta is lower than the set temperature T1 in step l2, the heater serving as the fixing roller heating means H1 is turned on (step n).
2) Go to step a2.

As described above, when the pressure roller has reached a predetermined temperature or higher, by stopping the control of the pressure roller heating means H2, it is possible to suppress a rise in the temperature of the pressure roller and prevent the image quality from deteriorating. As a result, it is possible to secure the feeding property and improve the durability of the rubber of the pressure roller. Further, the temperature of the pressure roller is detected, and when the temperature becomes equal to or higher than the predetermined temperature, the control of the pressure roller heating means H2 is stopped, and the fixing roller heating means H is stopped.
Only the temperature of the pressure roller 1 is controlled, and when the pressure roller falls below a predetermined temperature, the control of the pressure roller heating means H2 is returned again.

Next, the configuration of the image forming apparatus according to the seventh and eighth aspects will be described.

The image forming apparatus of this embodiment is similar to that of FIG.
, And the same configurations as those in the embodiment of FIGS. 1 and 2 are denoted by the same reference numerals and description thereof will be omitted.

The image forming apparatus of this embodiment includes a rotating unit 65 for rotating the fixing roller 100 and the pressing roller 200 under pressure, a fixing roller temperature detecting unit H1 for detecting the temperature of the fixing roller 100, Control means for driving the rotating means 65 until the fixing roller reaches a predetermined temperature. After the power is turned on, the fixing roller 10 is warmed up until the fixing roller 100 reaches a predetermined temperature.
The pressure roller 200 can be set to a higher temperature as a whole by rotating the pressure roller 200 and the pressure roller 200 under pressure and heating.

When the temperature of the fixing roller 100 reaches a predetermined temperature, the driving of the rotating means 65 is stopped, and an image formation permission signal is displayed on the display means 66. When the temperature of the fixing roller 100 is completely warmed up, the pressure roller is also completely warmed up, so rotation and heating are stopped, and copying is possible. During the warm-up, noise is generated by separating the fixing rotation drive and the conveyance drive. The image formation permission signal may be displayed on the display means 66.

That is, during the warm-up, as shown in FIG. 12, the fixing roller 100 and the pressure roller 200 are pressed and rotated and heated by the internal heaters of the fixing roller heating means H1 and the pressure roller heating means H2. The pressure roller was set to a higher temperature overall. When the warming-up of the fixing roller temperature is completed, the warming-up of the pressure roller is also completed.

During warm-up, noise may be reduced by separating the fixing rotation drive and the conveyance drive.

As an example of the image forming apparatus of this embodiment, the fixing roller has a cored bar of 13 mm and an internal heater 113.
0 W, set temperature 200 ° C., pressure roller: core metal thickness 5 mm, rubber thickness 5 mm, internal heater 280 W, set temperature 120-160 ° C., oil application roller: Nomex brush, oil application amount: 0.1 ０．２0.2 mg / copy, warm-up was 7 minutes, and the ambient temperature was 20 ° C.
The temperature of the pressure roller becomes as shown in FIG. 13, and by performing heating and rotation of the internal heater, the detection temperature of each part of the rubber is higher than that of only the internal heater or only the rotation, and the inner surface is The temperature difference with the outer surface is reduced.

By setting the temperature inside the pressure roller to an appropriate temperature, there is no fixing failure at the time of continuous copying, and a temperature sensor of the pressure roller is not required, so that downsizing, improvement in assemblability, and cost reduction can be achieved.

Next, the configuration of the image forming apparatus according to the ninth and tenth aspects will be described.

The image forming apparatus of this embodiment is similar to that of FIG.
, And the same configurations as those in the embodiment of FIGS. 1 and 2 are denoted by the same reference numerals and description thereof will be omitted.

In the image forming apparatus of this embodiment, an image forming means 71 for forming a toner image on an image carrier and a pair of rollers facing each other are conveyed while being conveyed, and the image on the recording medium is heated and pressed. The image forming apparatus includes a fixing unit H for fixing, and a rotating unit 65 for rotating a pair of rollers. The latent image forming means 70 is controlled by the writing unit 20 in FIG.
Thus, an electrostatic latent image corresponding to the image of the document D is formed on the photosensitive drum 31. Image forming means 7
1 includes a writing unit 20, a photosensitive drum 31, a charging unit 32, a developing unit 33, a static eliminator 36, a cleaning unit 39, and the like other than the transfer unit 34, the separator 35, and the fixing device 37 in FIG.

The control means K of the image forming apparatus drives the rotating means 65 after the power is turned on, and stops the driving of the rotating means 65 when the image forming means 71 is driven. As described above, after the power is turned on, the rotation unit 65 is driven, the driving of the rotation unit 65 is stopped when the image forming unit 71 is driven, and the rotation of the roller pair of the fixing unit H is stopped during the warm-up of the power required for image formation. By reducing the power consumption of the fixing heater or reducing the power consumption of the fixing heater, the power required for image formation can be supplemented.

The control means K of the image forming apparatus comprises at least one heating means of the fixing means H and the image forming means 7.
At the time of one drive, the amount of power supply to the heating means is controlled. By controlling the amount of electric power supplied to the heating unit when the image forming unit 71 is driven, power consumption can be efficiently used during image formation during warm-up, and power can be saved.

In the embodiment of the image forming apparatus according to the present embodiment, the fixing roller comprises a first heater L1 (900 W),
The heater L2 (230W), the pressing roller is a third heater L3 (280W), and the fixing roller rotates (30 to 5).
0W).

By digitizing, image forming conditions are corrected by forming an image before copying. As shown in FIG. 15, the required power during image forming (correction) is reduced by rotating the fixing roller pair during warm-up. The power required for image formation was compensated by stopping the power supply and reducing the power consumption of the fixing heater as shown in FIG.

The embodiment of FIG. 15 is shown in Table 4 and shows the driving status of the heater and the fixing roller in each mode (during warm-up).

Table 4

[0099]

The term "correction" refers to a process of rotating a photosensitive member or a developing unit to form a latent image or forming a toner image to perform potential correction, maximum density correction, or image gradation curve correction. Is measured, and each image forming condition is corrected so as to approach an optimum value.

The embodiment of FIG. 16 is shown in Table 5 and shows the heater usage status (during warm-up) in each mode.

Table 5

[0103]

As described above, the power consumption can be efficiently used during the image formation during the warm-up, and the power can be saved.

[0105]

As described above, according to the first aspect of the present invention, the fixing roller heating means and the pressure roller heating means are turned on and off based on the detected temperature of the fixing roller.
It is possible to control the set temperature to be high while reducing the overshoot of the pressure roller without detecting the temperature of the pressure roller. Further, since a temperature sensor for the pressure roller is not required, miniaturization, improvement in assemblability, and cost reduction can be achieved.

According to the second aspect of the present invention, the on / off timing of the pressure roller can be easily set.

According to the third aspect of the invention, the power supply amount is increased and the pressure roller temperature is set high by delaying the off-timing of the pressure roller heating means from the off-timing of the fixing roller heating means. Can be.

According to the fourth aspect of the present invention, the pressure roller heating means uses the ON / OFF cycle of the fixing roller to change the ON time of the pressure roller in accordance with a change in the ON / OFF cycle of the fixing roller. Therefore, overshooting of the pressure roller can be prevented, and the temperature can be controlled to a high temperature. Therefore, it is possible to prevent image defects during continuous copying while ensuring the durability of rubber.

According to the fifth aspect of the present invention, when the pressure roller has reached a predetermined temperature or higher, by stopping the control of the pressure roller heating means, it is possible to suppress an increase in the temperature of the pressure roller. The image quality can be prevented from lowering, the feeding property can be ensured, and the durability of the rubber of the pressure roller can be improved.

According to the sixth aspect of the present invention, the temperature of the pressure roller is detected, and when the temperature exceeds a predetermined temperature, the control of the pressure roller heating means is stopped, and only the temperature of the fixing roller heating means is controlled. If the temperature falls below the predetermined temperature,
The control of the pressure roller heating means is restored.

According to the seventh aspect of the present invention, after the power is turned on, during the warm-up period until the fixing roller reaches a predetermined temperature, the fixing roller and the pressure roller are pressed against each other and heated, so that the entire pressure roller is heated. A higher temperature can be set.

According to the eighth aspect of the present invention, when the temperature of the fixing roller is completely warmed up, the pressure roller is also completely warmed up. Therefore, the rotation and heating are stopped, and copying is possible. The noise may be reduced by separating the driving and the conveyance driving, and the image formation permission signal is displayed on the display unit.

According to the ninth aspect of the present invention, the rotating means is driven after the power is turned on, the driving of the rotating means is stopped when the image forming means is driven, and the rotation of the roller pair is stopped while the required power for image formation is warmed up. By doing so, the power required for image formation can be supplemented.

According to the tenth aspect of the present invention, by controlling the amount of electric power supplied to the heating unit when the image forming unit is driven, power consumption can be efficiently used during image formation during warm-up, and power can be saved. be able to.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an embodiment of an image forming apparatus.

FIG. 2 is a cross-sectional view illustrating a fixing device.

FIG. 3 is a diagram showing changes in roller surface temperature.

FIG. 4 is a diagram showing the surface temperature of a pressure roller.

FIG. 5 is a time chart of heating control.

FIG. 6 is a flowchart of heating control.

FIG. 7 is a cross-sectional view illustrating another embodiment of the image forming apparatus.

FIG. 8 is a time chart of heating control.

FIG. 9 is a diagram illustrating a fixing roller surface temperature, a detected temperature, and a heater energizing timing.

FIG. 10 is a flowchart of heating control.

FIG. 11 is a cross-sectional view illustrating another embodiment of the image forming apparatus.

FIG. 12 is a diagram showing a transition of a pressure roller surface temperature after warm-up.

FIG. 13 is a diagram showing the internal temperature of the pressure roller rubber.

FIG. 14 is a cross-sectional view illustrating another embodiment of the image forming apparatus.

FIG. 15 is a timing chart of control of the image forming apparatus.

FIG. 16 is a timing chart of control of the image forming apparatus.

[Explanation of symbols]

 Reference Signs List 100 fixing roller 200 pressure roller H1 fixing roller heating means H2 pressure roller heating means H fixing means S1 fixing roller temperature detection means S2 pressure roller temperature detection means K control means

Claims (10)

[Claims] A fixing roller having a fixing roller and a pressure roller disposed opposite to each other; a fixing roller heating means provided on the fixing roller; and a pressure roller heating means provided on the pressure roller. A fixing roller temperature sensor for detecting a temperature of the fixing roller in an image forming apparatus for nipping and conveying a recording medium between the fixing roller and the pressure roller and fixing the image on the recording medium by heating and pressing; Means for controlling the fixing roller heating means and the pressure roller heating means based on the detected temperature of the fixing roller. 2. The image forming apparatus according to claim 1, wherein the on / off timing of the pressure roller heating unit is based on the on / off timing of the fixing roller heating unit. 3. An image forming apparatus according to claim 2, wherein an off-timing of said pressure roller heating means is delayed from an off-timing of said fixing roller heating means. 4. The image forming apparatus according to claim 3, wherein the delay time varies depending on a time of an on / off cycle of the fixing roller heating unit. 5. A fixing device comprising: a fixing roller and a pressure roller disposed to face each other; a fixing roller heating device provided on the fixing roller; and a pressure roller heating device provided on the pressure roller. A fixing roller for detecting a temperature of the fixing roller in an image forming apparatus that fixes and fixes an image on the recording medium by heating and pressing the recording medium between the fixing roller and the pressure roller; Detecting means, pressure roller temperature detecting means for detecting the temperature of the pressure roller, and stopping the drive control of the pressure roller heating means when the detected temperature of the pressure roller is equal to or higher than a predetermined temperature, and heating the fixing roller. An image forming apparatus comprising: a control unit that controls only driving of the unit. 6. The driving control of the pressure roller heating means is performed again after the drive control of the pressure roller heating means is stopped and the detected temperature of the pressure roller is lower than a predetermined temperature. The image forming apparatus according to claim 1. 7. A fixing device comprising: a fixing roller and a pressure roller each having at least one heating unit disposed to face each other; and a rotation unit for rotating the fixing roller and the pressure roller by pressing. A fixing roller temperature detecting unit for detecting a temperature of the fixing roller in an image forming apparatus for nipping and conveying a recording medium between a fixing roller and a pressure roller and fixing the image on the recording medium by heating and pressing; A control unit that drives the rotating unit until the fixing roller reaches a predetermined temperature after power-on. 8. The image forming apparatus according to claim 7, wherein when the fixing roller reaches a predetermined temperature, the driving of the rotation unit is stopped and an image formation permission signal is displayed on a display unit. 9. An image forming means for forming a toner image on an image carrier, a fixing means for nipping and conveying a pair of rollers facing each other, and fixing the image on a recording medium by heating and pressing, and the roller pair. An image forming apparatus comprising: a rotating unit for rotating the image forming apparatus; and a control unit for driving the rotating unit after power is turned on, and for stopping the driving of the rotating unit when the image forming unit is driven. . 10. An image forming apparatus comprising: an image forming means for forming a toner image on an image carrier; and a fixing means for nipping and conveying a pair of opposed rollers to heat and press an image on a recording medium to fix the image. An image forming apparatus, comprising: at least one heating unit of the fixing unit; and a control unit that controls an amount of power supplied to the heating unit when the image forming unit is driven.